The run-up test is a known diagnostic test for ascertaining the injection quantity error for injectors in an internal combustion engine.
For example, a method for comparative testing of injection internal combustion engines is discussed in DE 10 2007 010 496 A1 in which the engine is controlled by an electrical engine controller which either has a self-diagnostic arrangement or is equipped with a connection interface for an external diagnostic device. Using the self-diagnostic arrangement or the diagnostic device, information may be obtained from the measured and displayable deviations of each of the defined measured variables by switching off one cylinder each, and may be indicative of a possible setpoint deviation of the switched-off cylinder. For example, the relative injection quantities of the individual cylinders may be inferred from comparing the maximum engine speed achieved during the run-up test. Starting from an idling speed, a certain number of injections are thereby activated using a predetermined fixed injection quantity so that the engine accelerates up. One individual cylinder is deactivated per test run. The relative injection quantity per test run may be inferred from the reached maximum engine speed.
However, since the torque requirement due to friction and other effects (e.g., power train elements connected to the engine) is not known, the absolute injection quantity may not be ascertained.
Therefore, for example, in the case of a four-cylinder engine, if a greater quantity was ascertained for two cylinders relative to the other two cylinders, it remains unclear whether the two cylinders with the smaller injection quantity have a quantity shortfall and the cylinders with the larger injection quantity inject the correct quantity, or whether the two cylinders with the smaller injection quantity inject the correct quantity and the cylinders with the larger injection quantity have an excess quantity. This means that it is not clear which injectors have to be exchanged.